1. Field of the Invention
This invention relates to a device for use in discharging a fluid from a fluid processing apparatus such as a spinning centrifuge bowl. In accordance with the invention, the discharge device is so designed as to permit its use in applications wherein only small amounts of surface turbulence are tolerable. In accordance with another aspect of the invention, the device is further designed for applications requiring low levels of surface turbulence and yet relatively high levels of sub-surface turbulence.
2. Description of the Prior Art
Many types of scoop devices for discharging fluid material from fluid processing apparatus are known in the art. The most common type of scoop device is the pipe scoop, or a variation thereof, which basically comprises a stationary pipe of suitable diameter bent such that the pipe opening is oriented to "scoop up" the fluid material moving past it. To improve upon the basic tube scoop design, certain modifications are common, such as tapering the pipe to increase the pressure of the discharged material, or adding a splash guard to catch the fluid material splashed as a result of surface turbulence. In addition, it is known to adjust the scoop level, i.e., the depth in the fluid material at which the scoop is positioned, whereby fluid material from a range of depths may be discharged. Also, efforts have been expended to streamline the basic pipe scoop design in order to reduce turbulence, thereby reducing levels of splashing and foaming.
A skimming tube is disclosed in U.S. Pat. No. 3,228,595 suitable for use in discharging a liquid from a spinning centrifuge bowl. As a result of a streamlined tube design, the skimming tube produces lowered levels of turbulence throughout the liquid. Reduced turbulence results in reduced splashing and foaming, thereby enabling the skimming tube to be employed in applications wherein foaming adversely affects the quality of the liquid. Cited examples of such liquids are orange juice which suffers a taste deterioration when aerated, and reducing agents such as photographic developers which lose effectiveness when mixed with air.
While the disclosed skimming tube is suitable for use with liquids such as orange juice and photographic developers, it does not function adequately when used with a viscous fluid. In this case, the viscous fluid does not flow into the leading openings as easily as it flows around the body. As a result, the viscous fluid tends to "back up" in front of the disclosed skimmer tube producing levels of turbulence and splashing which are unacceptable in certain applications for which the present invention is proposed.
In addition, unlike photographic developers, some types of fluids which are adversely affected by aeration and commonly discharged from fluid processing apparatus of the type including a spinning centrifuge bowl, are not solutions but rather suspensions or emulsions. In this type of fluid, particles originally dispersed throughout the liquid or gel tend to migrate, under the influence of centrifugal force, away from the center of the spinning centrifuge bowl. For use in these applications, the discharge device should not only be designed to produce minimal surface turbulence, but also should provide enough sub-surface turbulence, especially towards the bottom of the fluid, to keep the particles dispersed throughout the fluid, thereby inhibiting particle build-up along the bottom of the centrifuge bowl.
In the specification and accompanying claims the term "sub-surface" is used. Herein, sub-surface is understood to refer to any portion of the fluid substantially below the surface.